As is well known, a Web server, in response to an HTTP request from a client, establishes an HTTP connection (or HTTPS connection) to a Web application server and sends the HTTP request to the Web application server. The Web server receives an HTTP response from the Web application server in response to the HTTP request and forwards it to the client.
In general, the Web server makes a socket connection (or HTTP connection) to the Web application server, and in some cases, if the Web application server requests to use SSL encrypted communication, the Web server needs to make an SSL connection (or an HTTPS connection) to the Web application server.
Thereafter, the Web server may close the HTTP connection with the Web application server. If the Web server does not immediately close the HTTP connection, the Web applications server may shutdown the HTTP connection after a Keep-alive time has passed.
In other words, the Web server repeats a procedure that creates and closes an HTTP connection to the Web application server every time it receives an HTTP request from the client and creates and closes the HTTP connection again when a new HTTP request comes in from the client.
However, the frequent creation and closing of the HTTP connection every HTTP request from the client may result in an overhead on the Internet environment that requires high-speed response. Especially, the overhead may further increase in a case where the Web server makes an HTTP connection to the Web application server but needs an SSL connection (HTTPS connection) for the SSL encrypted communication.